Nanodiamond and a Method for the Production Thereof

ABSTRACT

The invention relates to carbon chemistry and is embodied in the form of a nanodiamond comprising 90.0-98.0 mass % carbon, 0.1-5.0 mass % hydrogen, 1.5-3.0 mass % nitrogen and 0.1-4.5 mass % oxygen, wherein the carbon is contained in the form a diamond cubic modification and in a roentgen-amorphous phase at a ratio of (82-95):(18-5) in terms of a carbon mass, respectively. The inventive method for producing said material consisting in detonating in a closed space of a carbon-inert gas medium a carbon-containing oxygen-deficient explosive material which is placed in a condensed phase envelop containing a reducing agent at a quantitative ratio between said reducing agent mass in the condensed envelop and the mass of the used carbon-containing explosive material equal to or greater than 0.01:1 and in chemically purifying by treating detonation products with a 2-40% aqua nitric acid jointly with a compressed air oxygen at a temperature ranging from 200 to 280° C. and a pressure of 5-15 MPa.

TECHNICAL FIELD

The given invention refers to the field of inorganic chemistry ofcarbon, to be exact, to diamond modification of carbon—Nanodiamond,possessing qualities of ultrahard material and method of its production,in particular, using detonation synthesis from carbon-containingexplosive mixes with further Nanodiamond extraction using chemicalmethods.

PREVIOUS TECHNICAL LEVEL

Various composition materials produced by methods of detonationsynthesis from carbon-containing explosives and containing carbon invarious phases are known. Nanodiamond is formed at detonation ofcarbon-containing explosives with negative oxygen balance in specialconditions in environment allowing to preserve it.

Nanodiamond is n individual particle from 2 to 20 nm in size, utilized,as a rule, in bigger particles ensembles. Due to its nanosizeNanodiamond posses high dispersion level, defects of surface structuresparticles, and consequently, active surface. These characteristics mayvary in quite wide ranges depending on Nanodiamond productionconditions.

Experts in the field of carbon chemistry are well aware for almost 20years about Nanodiamond of classical elemental composition, mainlycontaining carbon in cubic diamond phase with the following elementsstructure, mass. %: carbon—72-90; hydrogen—0.6-1.5; nitrogen—1.0-4.5 andoxygen—4-25; and methods of its production (Volkov K. V., Danilenko V.V., Elin V. I. Diamond synthesis form carbon VV detonation products,Burn and explosion Physics, 1990, t.26, N° 3, p. 123-125; Lyamkin A. I.,Petrov E. A., Ershov A. P. and others. Diamond acquisition fromexplosive materials, DAN USSR, 1988, t.302, p. 611-613; Greiner N. R.,Phillips D. S., Johnson F. J. D. Diamonds in detonation soot, Nature,1988, vol. 333, p. 440-442; Petrov V. A., Sakovich G. V., Brylyakov P.M. Diamonds keeping conditions at detonation, DAN USSR, 1990, t.313,N°4, p. 862-864; V. Y. Dolmatov. Superdispersed diamonds of detonationsynthesis: characteristics and use, Chemistry progress, 2001 t.70 (7),p. 687-708; V. Y. Dolmatov. Superdispersed diamonds of detonationsynthesis, St. Petersburg, SPbGPU, 2003, 344 p).

The properties of classic Nanodiamond are fully described. (V. Y.Dolmatov. Superdispersed diamonds of detonation synthesis:characteristics and use, Chemistry progress, 2001 t.70 (7), p. 687-708;V. Y. Dolmatov. Superdispersed diamonds of detonation synthesis, St.Petersburg, SPbGPU, 2003, 344 p; EP, 1288162, A2,).

Carbon chemistry experts are aware of the condensed carbon(CC)—composition carbon material, containing carbon in variousmodifications and, depending on conditions of detonation ofcarbon-containing explosives containing or not containing carbon incubic diamond phase.

Such CC can be produced at detonation of carbon-containing explosiveswith negative oxygen balance in special environment under conditionsallowing to preserver condensed carbon products of explosion. (LyamkinA. I., Petrov E. A., Ershov A. P. and others. Diamond acquisition fromexplosive materials, DAN USSR, 1988, t.302, p. 611-613; Greiner N. R.,Phillips D. S., Johnson F. J. D. Diamonds in detonation soot, Nature,1988, vol. 333, p. 440-442; Petrov V. A., Sakovich G. V., Brylyakov P.M. Diamonds keeping conditions at detonation, DAN USSR, 1990, t.313,N°4, p. 862-864; V. Y. Dolmatov. Superdispersed diamonds of detonationsynthesis, St. Petersburg, SPbGPU, 2003, 344 p V. Y. Dolmatov.Superdispersed diamonds of detonation synthesis, St. Petersburg, SPbGPU,2003, 344 P).

It is known that CC production method may include blast ofcarbon-containing charge in various environments, for example:

-   -   in gas environment, inert to carbon, for example in nitrogen        environment, carbonic acid, light-end products of previous        blast. (U.S. Pat. No. 5,916,955, C1);    -   in water foam (Petrov V. A., Sakovich G. V., Brylyakov P. M.        Diamonds keeping conditions at detonation, DAN USSR, 1990,        t.313, N° 4, p. 862-964);    -   charge water irrigation (RU, 2036835, C1);    -   in water cover (U.S. Pat. No. 5,353,708, C1);    -   in ice (RU, 2230702, C1).

Out of all existing methods of carbon-containing explosive materialsdetonation, the most effective from the view point of CC and diamondmodification output is charge blast in water or ice cover (V. Y.Dolmatov. Superdispersed diamonds of detonation synthesis, St.Petersburg, SPbGPU, 2003, 344 p; RU, 2230702, C).

The CC received is a nano-dispersed carbon-containing powder, possessingspecific characteristics and structure. For example, CC is distinguishedby high dispersion ability, wide specific surface, presence of newlycreated carbonic faulted structures, increased reactivity.

There is synthetic diamond-carbon-base material (U.S. Pat. No.5,861,349, A), consisting of grouped round and irregular shapedparticles in diameters diapason not exceeding 0.1 M, where: a) elementcomposition of mass. %: carbon from 75.0 to 90.0; hydrogen from 0.8 to1.5; nitrogen from 0.8 to 4.5; oxygen—up to balance; b) phasecomposition, mass. %; amorphous carbon from 10 to 30, cubic modificationdiamond—up to balance; c) material porous structure, the volume of pores0.6-1.0 sm³/gr; d) material surface with existence of over 10-20% ofsurface of throwing, nitrite, primary and secondary hydroxyl groups,possessing various chemical shifts in the field of NMR spectrum and oneor more oxy carboxylic functional groups, selected from the group ofconsisting of carbonylic groups, carboxylic groups, guanine groups,hydroperoxide and lactones groups over 1-2% of material surface relatedto carbon atoms by noncompensated connections; and e) specific surfacefrom 200 to 450 μM²/g.

Above mentioned material is produced by detonation synthesis method inthe closed volume of explosive charge, which mainly containscarbon-containing explosive material or mix of such material, possessingnegative oxygen balance. The charge detonation is initiated in presenceof carbon particles with concentration from 0.01 to 0.015 kg/m³ inenvironment, consisting of oxygen from 0.1 to 6% in volume and gas,inert towards carbon, at temperature of from 303 to 363 K. (U.S. Pat.No. 5,861,349, A). This method is carried out in pressure chamber withcharge of negative oxygen balance, consisting mainly of, at least, onecarbon-containing solid explosive.

10-20% of material surface are occupied by metal- nitrile-, primary andsecondary hydroxyl groups and also oxycarboxyl and functional groups ofgeneral formula O.dbd.R, where R— is .dbd.COH, .dbd.COOH,.dbd.C.position 6H. position.4 or other combinations, besides 1-2% ofmaterial surface is occupied by carbon atoms with noncompensatedconnections.

Parameter—lattice distance—is as =0.3562+0.0004 nm, content ofnonflammable impurities is from 0.1 to 5.0 mass. %.

The x-ray amorphous phase of the received material does not containgraphite.

Oxygen-containing functional groups, as a rule, are derivatives ofvarious surface carbon structures, including aliphatic, alicyclic andaromatic. Both lacton.dbd.COOCCΓ, quinine.O.dbd.C pol. 6H.pol.4H.dbd.O,and hydroperoxide.dbd.COOOH groups were identified on surface of theproduced material. Total quantity of oxygen-containing surface groupstakes from 10 to 20% of sample surface.

However, the above mentioned method of diamond-carbon materialproduction has low output of diamond-carbon material—3.1-5.1 mae. % anddoes not allow to receive material with high efficacy and of highquality, as due to low content of carbon—the most important element indiamond-carbon material—the end product contains large quantity ofheteroatom, mainly oxygen, existing in form of lactone, etheric andaldehyde groups that leads to excessive chemical activity ofdiamond-carbon material. This fact increases possibility of destructiveprocesses in compositions with use of diamond-carbon material, e.g. inpolymerous and oil compositions, especially at elevated operatingtemperature.

Low (from 9.1 to 58.4 mass. %) content in produced condensed carbon ofthe main component of Nanodiamond—cubic modification diamond—makes thefollowing chemical refinement of Nanodiamond complicated. Moreover,Nanodiamond properties are worsening due to considerable, ˜2.3 mass. %,quantity of nonflammable impurities in chemically refined Nanodiamond.The above mentioned patent (U.S. Pat. No. 5,861,349, A) shows only onemethod of material production using one composition of explosive—mix oftrotyl and cyclonite with 60/40 ratio respectively. This does not allowto evaluate all advantages of above mentioned method of diamond-carbonmaterials production.

There is Nanodiamonds, produced by detonation synthesis, refinementmethod, with following impurities refinement (RU, 2109683, A) usingtwo-stage treatment of detonation products by water solution of nitricacid: first 50-99%—nitric acid at 80-180° C., then 10-40%-nitric acid at220-280° C. Liquid phase behavior of the process is provided bypressure. However this method is not used widely due to high aggressionand corrosion activity of used concentrated nitric acid, its largeconsumption, complicacy of utilization and neutralization of gauzy andliquid wastes.

The closest analogue for this Nanodiamond refinement method is onedescribed in literature (Gubarevich T. M., Dolmatov V. Y. Chemicalrefinement of diamonds by hydrogen peroxide. Applied Chemistry magazine.1992, t.65, N° 11, p. 2512-2516). The method consists of treatment ofdetonation products, containing nanodiamonds, by oxidizing solution,including hydrogen peroxide, nitric acid or variable valency metal salt.This method disadvantage is in use of expensive and rareoxidizer—hydrogen peroxide, danger of operating with such easilydecomposing combination, constantly emitting very active oxidizer—atomicoxygen.

Invention disclosure.

The objective of the given invention is developing Nanodiamondproduction method, —safe, reliable, characterized by improved technical,economical and ecological parameters and allowing to organize wideproduction of nanodiamonds, possessing predictable qualities andpredictable elemental composition with high carbon content in desiredphase conditions.

During invention development the objective was set to develop the methodof producing nanodiamond, possessing high concentration of carbon ofdesired modifications and desired phase composition from carbon-basematerial using detonation synthesis under conditions preventingoxidation of nanodiamond surface and providing safety of the acquireddiamond phase.

The objective was achieved through production of diamond-carbonmaterial, containing carbon, hydrogen, nitrogen and oxygen. Itsdistinction is that material contains carbon in form of diamond cubicmodification and in x-ray amorphous phase with ratio (82-95): (18-5)according to carbon mass, respectively, and contains, mass. %:

Carbon 90.2-98.0 Hydrogen 0.1-5.0 Nitrogen 1.5-3.0 Oxygen 0.1-4.5.

The objective was achieved through development of method of productionof nanodiamond, containing detonation of carbon-containing explosivewith negative oxygen balance in closed volume in gauzy environment inerttowards carbon, in condensed phase surrounding, distinguished bycarrying out detonation of carbon-containing material explosive put intocondensed phase cover, containing deoxidizer at quantitative ratio ofdeoxidizer mass in condensed phase to mass of the used carbon-containingexplosive not less then 0.01:1. Chemical refinement is applied bytreating detonation products by 2-40% water nitric acid alone withcompressed air oxygen at temperature of 200-280° C. and pressure 5-15MPa, and produce Nanodiamond, containing mass. %:

Carbon 90.2-98.0 Hydrogen 0.1-5.0 Nitrogen 1.5-3.0

Oxygen 0.1-4.5 containing diamond cubic modification carbon and x-rayamorphous phase carbon in ration (82-95): (18-5) mass. %, respectively.

It is reasonable, according to invention, to use as deoxidizer organicor inorganic compounds, preferably those not containing oxygen andhalogen atoms.

Further, the given invention is explained with help of examples of itsrealization, however, not limiting possibilities of the methodrealization and not stepping out the patent claims.

The best way of invention realization.

The process of nanodiamonds formation by method according to invention,including detonation of carbon-containing explosive with negative oxygenbalance, surrounded by condensed phase containing deoxidizer can bedivided into four stages.

1. Stage one. Detonation transformation of carbon containing explosiveat blast mainly happens in range of charge volume, limited by its outersurfaces, but charge surrounding environment does not influence theprocess of transformation.

According to research results, explosive materials with negative oxygenbalance leads to creation of “extra” carbon, which remains in condensedform. Part of this “extra” carbon transfers into cubic modificationdiamond after explosion.

Charge placement into environment of liquid or solid aggregatecondition, e.g. when blown up in the pool filled with water or ice thatprevents detonation products throwout, creates conditions for increasedlength of existence of high pressure and temperature complex created atdetonation, which is existence environment for diamond and liquidcarbon.

Charge placement inside the condensed phase, both liquid or solidaggregate condition, containing cover, e.g. in form of ice or water alsoallows to keep the detonation products for longer time in the volume ofprimary charge, which leads to prolonged existence of plasma, containingdetonation products, and contributes to better transformation of “extra”carbon into diamond phase.

2. Stage two. This transformation stage starts after the detonationprocess completes. It is very important to provide fast gas-dynamiccooling of detonation products for preservation of cubic modificationdiamonds, created in chemistry transformation zone.

It is known that due to explosion in vacuum, the fastest gas-dynamiccooling of detonation products takes place due to high speed ofthrowout. However, kinetic energy of detonation products transforms intoheat energy as they blow the walls of the explosive chamber.

Chamber temperature goes up fast achieving very high values and aftercalming down of all blows inside the chamber the temperature sets up for˜3500 K—close to detonation temperature. The cubic modification diamondsfully transform into graphite, as chamber pressure drops times fasterthen chamber temperature. After that all CC gasify due to prolongedinfluence of high temperatures that is why cubic modification diamondsdo not preserver in vacuum explosion.

The slowest gas-dynamic cooling exists at detonation products throwoutsurrounded by massive ice or water covers. So maximum set temperature ofdetonation products does not exceed 500-800K due to effective energyextraction by water (RU, 2230702, C; V. A. Mazanov. Macrokinetics ofcondensed carbon and detonation nanodiamond preservation in hermeticexplosive chamber, solid body physics, 2004, t.46, iss.4, p. 614-620).

The gas-dynamic cooling intensity of explosion in inert gas environmenttakes middle value between vacuum explosion and condensed phase, in formof water or ice, cover explosion, as speed of detonation productsthrowout in gas environment is lower then in vacuum but higher then inwater and ice cover.

As CC existence is determined mainly by residual temperature inexplosive chamber—the lower the temperature, the higher thediamond-carbon material output—then the use of condensed covers aroundthe charge seems to be the best since they create the highest coolingrate.

3. Stage three of detonation synthesis of diamond-carbon material comesafter shock waves reflection from the chamber walls: circulation ofshock waves, spreading with supersonic speed and accompanied byprocesses of sharp increase of substance density, pressure andtemperature, and turbulent mixing of detonation products withenvironment inside the chamber takes place. The maximum set temperatureof environment inside the chamber depends on ration of explosive massand gas components, i.e. chemical environment activity and gases heatcapacity.

4. Stage four. The environment, heat by explosion of carbon-containingexplosive and limited by cool cover—is cooling intensively. Afterexplosion and detonation products release, chamber contains both variouskinds of gauzy products (CO₂, CO, O₂, H₂, N₂, CH₄, NO, NO₂, NH₃, H₂O),and highly dispersed suspension of CC particles possessing high radiatecapability. Thus the process of such environment cooling ischaracterized by combined heat transfer through convection and emission

Using the method of electroconductivity profile measurement indetonation wave they determined that time of cubic diamond modificationformation does not exceed 0.2-0.5 mcs, which corresponds to the width ofchemical reaction zone in mix compositions of trinitrotoluene-cycloniteexplosions, both pressed and lithium (Staver A. M., Ershov A. P.,Lyamkin A. I. Research on detonation transformation of condensedexplosives by electroconductivity method. Physics of burn and explosion,1984 t.20, Ks 3, p. 79-82).

As part of formed on the first stage of detonation solid CC particlestransforms into gases under the influence of gauzy oxidizers formed byexplosion: CO₂, H₂O, CO, O₂, N₂O₃, NO₂, we can talk about preservedparticles CC that didn't succeed to gasify, including due to lack ofabove mentioned oxidizers number.

Any non responded solid particles of CC carbon have functional groupscover. Thus interaction of surface functional groups with gauzyoxidizers is capable to change primary functional groups, including nonoxygen containing for oxygen containing, as all oxidizers containoxygen.

The use of important deoxidizer function—tie oxidizer, preventing carbonoxidation, creates conditions for preventing carbon particles surfacesfrom oxidation. Thus, creating conditions for considerable increase ofcarbon content in nanodiamond. This increase is being achieved throughdecrease in oxygen content, as following research results, content ofnitrogen and hydrogen changes insufficiently.

We should also note the fact that high content of oxygen in nanodiamondsprevents it from efficient use in some technologies. For example, whenusing diamond-carbon material as additives to oil, availability of largequantity of oxygen increases oxidizing capability of material.

Maximum output of CC—12%—is achieved by explosion of carbon-containingmaterial in gas chamber under conditions of set temperature of1500±150K. Increasing the temperature in chamber till 3000-3500K we willdecrease the output till zero. (V. A. Mazanov. Macrokinetics ofcondensed carbon and detonation nanodiamond preservation in hermeticexplosive chamber, solid body physics, 2004, t.46, iss.4, p. 614-620).

Preservation possibility of received diamonds of cubic modification andelemental composition of diamond-carbon material depends on intensity ofhetero-phase endothermic reactions of CC gasification by carbon dioxide(1) and water steam (2) behavior in gas chamber that can be presented assingle gross-reaction (3):

C+CO₂>2CO-172.4 kJ/mole  (1)

C+H₂O>CO+H₂-130.1 kJ/mole  (2)

C+CO₂+H₂O>3CO+H₂-151.3 kJ/mole  (3)

Two competing processes occur in explosive chamber under hightemperature: CC gasification—non-diamond carbon in the first turn asmore active, and graphitization of formed diamonds of cubicmodification.

Thus authors found it reasonable to develop conditions of synthesiscarrying out that would provide minimal influence possibilities ofdetonation products onto received, at detonation, product and maximumpossible speed of product cooling to prevent its gasification. Followinginvention, the input of deoxidizer into condensed cover of the chargeallows achieving several effects:

1. Deoxidizer prevents carbon particles surface from oxidation in thethird stage of detonation process, by tying oxidizers as the most activechemical components inside the chamber. As a result, content of the mainheteroatom-oxygen, preventing further use of CC, sharply drops till0.1%, and its place is taken by quite inert and neutral hydrogen. Carboncontent increases to 95.2%.

2. The chamber temperature drops sharply due to partial decomposition ofoxidizer under high temperatures, which in turn, decreases gasificationprocess (reactions 1-3) and “freezes” phase transformationdiamond-graphite.

Thus deoxidizer input allows increasing nanodiamonds output in 1.7-2.6times in comparison to nanodiamonds output 3.1-5.1% using knowntechnology (U.S. Pat. No. 5,681,459, A).

Any organic or inorganic compositions possessing deoxidizer qualities,mainly those not oxygen- and halogen-containing and showing expresseddeoxidizer qualities, can be used as deoxidizer.

Intermediate product, produced in result of detonation synthesis ishighly dispersed condensed carbon (CC), containing not onlynanodiamonds, but also non-diamond carbon in high reactivity form, isundergoing chemical treatment according to invention.

Nitric acid is quite powerful oxidizer for non-diamond carbon.

The interval used for nitric acid concentration refinement 2-40 mass. %was determined experimentally, according to technologically acceptablespeeds of reaction. Lowering concentration below 2% leads toproductivity decrease. Increasing nitric acid concentration over 40% isunreasonable due to increased number of acid waste and increasingcorrosion activity of environment.

In case we treat CC by nitric acid with concentration of 2-40 mass. %only with all other technological conditions unchanged (t=200-280° C.and P=5-15 MPa), refinement quality will be very low and the purity ofproduced nanodiamond will not exceed 85%.

Using concentration of nitric acid 2 mass. % one should maintaintemperature 280° C., pressure 12-15 MPa due to compressed air (properpressure of 2% nitric acid is 6.5 MPa). Conditioning time—one hour. Thepurity of produced nanodiamond—98.7%.

For 40% mass nitric acid it is enough to maintain temperature 200° C.and pressure 5 MPa due to compressed air (proper pressure of 40% nitricacid is 2.9 MPa). Conditioning time is 40 min. The purity of producednanodiamond 99.2%.

Compressed air secures surplus pressure and ultrabalanced oxygencontent, and also high speed of nitric acid regeneration in the system.The value of surplus pressure is 2-9 MPa, created by compressed air,secures both physical conditions (liquid-phase of the system) andcompecated material balance between gauzy and compensated components ofthe system. System's general pressure interval is 5-15 MPa isexperimentally determined field of process behavior.

Compressed air input into oxygen oxidation system creates the bestconditions for oxidation process. Non-diamond carbon oxidation products—CO₂, NO₂H NO—evolve into gauzy phase. The processes of nitric acidregeneration behave on the following scheme at simultaneous surplus ofcompressed air in solution and gauzy phase:

2NO+O₂→2NO₂̂N₂O₄

4NO+3O₂+2H₂Ô4HNO₃

4NO₂+O₂+2H₂O+±4HNO₃

Newly created nitric acid comes into reaction with non-diamond carbon.The oxidation system in question can also oxidate main non-carbonimpurities in CC—iron, copper, their oxides and some carbide. The giveninvention can be illustrated by examples of nanodiamond productionmethod realization according to invention, including method of condensedcarbon production and its following chemical treatment and production ofnanodiamond with improved qualities. Mix carbon-containing explosivesare usually used for CC synthesis, e.g. mix of trinitrotoluene andhexogen or octogen with trinitrotoluene content form 30 to 70%. It isalso possible to use trinitrotriaminbenzol mixed with trinitrotoluene,hexogen or octogen.

The following was chosen for tests of carbon containing explosives:

-   -   charges from mix of trinitrotoluene and hexogen, formed by        pressing under pressure of 1500 kg/sM ² with ratio 50/50        (examples 1-18) and melting with ratio 65/35 (examples 19.20);    -   charges from mix of trinitrotoluene and octogen, formed by        pressing under pressure of 1500 kg/sM ² with ratio 60/40        (example 21);    -   charges from mix of trinitrotriaminbenzol and octogen, formed by        pressing under pressure of 1500 kg/sM ² with ratio 50/50        (example 22). Traditional charge form was chosen—solid cylinder,        and cylindrical cartridge diameter—48.5 mm, charge length—167, 1        mm.

Charge blasting was realized using electrodetonator, located from thebutt end inside the charge.

The charge of carbon-containing explosive was put into condensed phasecover—solution of deoxidizer in water in liquid aggregate condition(examples 1-16, 18, 19, 21, 22) or in ice condition (example 20), or incover produced as charge armor from pressed solid deoxidizer (example17). The cover mass is from 4.0 to 6.0 kg. The covers, in liquidaggregate conditions, were cylindrical polyethylene bags, filled withcondensed phase of deoxidizer solution and charge, hanged inside thebag. In case of solid aggregate condition of the cover with use ofadamantan as deoxidizer, the cover looked like outer armor over entiresurface.

The following was used as deoxidizers: dimethylhydrazine (examples 1-5,19), urotropine (examples 6-10, 20-22), ammonia (examples 11-13),carbamide (examples 14-16), adamantan (example 17), acentonitrile(example 18) with different, in range of (0.01-10.0): 1.0, correlationof mass of used deoxidizer and mass of used explosive correspondingly.

The tests were carried out the next way: covered charge was placed intoexplosive chamber through upper hatch. The explosive chamber is made ofstainless steel, volume of 1 m³, filled with gauzy products of previousblasting. The chamber was closed then and charge blasted.

In three minutes after blast the unloading of received water suspensionwas realized through the lower valve into receiving capacity. Watersuspension then was passed through 200 mcm sell sieve and dried. Driedproduct was crushed and sifted through 80 mcm sell sieve and afterwardsthe samples of the received product were prepared for further researchof their elemental composition according to invention method.

Received product was put into titanic autoclave with 56% nitric acidwith estimation of 1 part of received product for 20 parts of acid.Autoclave was heated up to 513K and kept at this temperature for 30minutes. Then autoclave is cooled, gases were bleeded, productsuspension in work off weak nitric acid was retrieved. Nanodiamonds werewashed in distillated water till pH 6-7 and air dried at temperature of423K for 5 hours.

Samples of the received product were prepared for further research oftheir elemental composition according to invention method.

Researches have determined that diamond-carbon material contains from 8to 14 mass % of volatile impurity (mainly water, nitrogen oxides andhydrogen oxides). Removal of such impurities, hardly tied by adsorptiveforces in micropore, by ordinary air heating at temperatures 120-125° C.is impossible.

Heating temperature increase to higher temperatures is dangerous due todecomposition and flammability of particles of non diamond carbon. Tocompletely remove volatile impurities one should use vacuum withresidual pressure 0.01-10.0. The temperature should be maintained in therange of 120-140° C.

Temperature 120° C. is sufficient in vacuum 0.01 Pa, and 140° C. in 10.0Pa vacuum. It is unreasonable to maintain pressure less then 0.01 Pa dueto economical reasons, and higher then 10.0 Pa—due to possible notcomplete removal of volatile impurities. Increasing temperature beyond140° C. may cause decomposition of part of unstable non-diamond carbon.The heating time of 3-5 hours guarantees complete removal of volatileimpurities. Three hours is enough at 0.01 Pa and 120° C., whereas fivehours needed at 10.0 Pa and 140° C.

The standard methodology from organic chemistry is usually used todetermine elemental composition of nanodiamond: heating temperature inoxygen flow is 850-900° C. during 5 s. However nanodiamond differs a lotby its resistance towards oxidation from any organic compounds. Thusconditions stated above are not enough for complete oxidation of theelements forming nanodiamond. The temperature providing full oxidation(burn) of nanodiamond is 1050-1200° C., and heating time to be 40-50seconds. These conditions can be achieved using device JYo 185 of“Hewlett Packard” (USA).

Samples of received products were sustained at 120-140 C temperature invacuum 0.01-10.0 Pa for 3-5 hours and undergo to treatment by the oxygenflow under the temperature of 1050-1200° C. with speed providing itsburning for 40-50 sec.

Samples of synthesis products, prepared by method described aboveundergo the following tests:

-   -   Research using small-angle dispersion method for determination        of quantitative distribution of particles of material over its        size;    -   Research using polarographic titration for determination of        existence and composition of surface, oxygen-containing, amine        and amide functional groups. The amine, amide, hydroxyl,        carboxyl groups are identified by value of corresponding        reduction potentials and IR-spectroscopy data;    -   Research using gas-chromatographic analysis for existence of        surface throwing groups, identified by composition of emitted        gas at heating, at temperature 663-673K during 3 hours, per        quantity of emitted methane. The achieved products were heated        at 473 K in vacuum (0.1 Pa) until achieving the product of        constant weight (during 24 hours) before gas-chromatographic        analysis. During the heating process previously absorbed by        received product surface volatile products, including gases,        were eliminated, and emitted at gas-chromatographic analysis        gases CH₄, H₂, CO₂, CO, O₂, N₂ and NH₃ were gases forming at        destruction of chemically connected with CC surface groups;    -   Research using x-ray photoelectron spectroscopy (XPES) to        analyze the distribution of carbon forms in achieved product;    -   Research using small-angle dispersion method (Svergoon D. I.,        Feigin L. A. x-ray and neutron small-angle dispersion, Moscow,        izd <<Nauka>, 1986, 280 p);    -   Research using determination of specific surface using powder        means of low-temperature sorption nitrogen method (further BET)        (Gerasimov Y. M. and others. Physical Chemistry. T. L, edition        2., Moscow, izd. <<Chemistry>>, 1969, p. 592).

Research results are shown in Table.

Table

Production of nanodiamond according to invention by the means ofinvention

Extension of table 1Extension of table 2Extension of table 3Extension of table 4Extension of table 5

Researches have discovered that nanodiamond, produced by method ofinvention is powder from light grey to grey color.

Based on polarographic, chromatographic and IR-spectroscopic analysis,the structure of surface functional groups was determined: hydroxyl,carboxyl, carbonyl, amide, nitric, and methane groups were discovered inall samples received in the process carried out according to invention.

X-ray pictures of nanodiamond(Cu K_(α)), produced by mentioned method,show wide symmetrical, well described by Lorenzo's counters diffractionmaximums at angles of 2H)=43.9; 75.3 and 91.50 corresponding to (111)-,(220)- and (31 l)-reflections from the grid of cubic modificationnanodiamond with grid parameter a₀=3.565±0.002 A. Average size ofproduced nanoparticles—4.0-5.0 shp. indicates that widening ofdiffraction maximums is mainly connected to small particles size, notinternal tension.

Strong allocated halo is observed in the range 2Λ=16°-37° that typicalfor diffraction on random amorphous structures, confirming the presenceof x-ray amorphous carbon phase. This structures thickness estimation onhalo half-width is 2-4 A, that is 5-18 mass. % from nanodiamond weight.Besides quantity of amorphous phase was determined from decrease inreflection intensity till 220 nanodiamond according to given inventionin comparison to sample of pure natural cubic diamond (Yakutia-Sakha,set. Mirnyi, Russian Federation). X-ray amorphous phase estimatedquality is from 5 to 18 mass. %. Existence of ˜2.5 mae. % nitrogen inamorphous phase is determined as follows.

Nanodiamond hinged, produced by method according to given invention, washeated at 473 K for 20 hours in vacuum in 0.1 Pa until constant weight.Then, different parts of this hinge undergo deep extraction by variousdissolvents at temperature of 473-573K under pressure during 3 minutes.Dissolvent used: normal structure—heptane, decane; aromatic—benzol,toluol, alicyclic-cyclohexane-carbon; hydro-naphthalene—tetralyne anddecalyne. The ratio of diamond phase of carbon, which does not changeunder such conditions, and amorphous phase, which has decreased, aftersuch treatment was changed. Nanodiamond samples weight has lowered for˜5 mass. %. Only nitrogen-bearing heterocyclic aromatic compositionswith number of cycles from 1 to 4 and nitrogen content in circles 1-2have passed into solution of above mentioned dissolvents. No otherheteroatom in any form was found in solution. IR-specters have shown innanodiamond after extraction all the same surface oxygen, hydrogen,nitrogen-containing groupings placed there before extraction. Thus,nitrogen in form of heterocyclic compositions was definitely suppliedfrom middle layer—x-ray amorphous phase of carbon.

Moreover, complicacy of x-ray amorphous phase of carbon structure innanodiamond demonstrates the fact that when similarly nanodiamondssamples according to invention (mode: 473K, 20 hours, 0.1 Pa) undergothermal desorption under sift conditions (mode: 573K, 2 hours, 0.001Pa), desorption products content was diverse: acentonitrile,nitromethane, butanone—on and butanone-2—on; tetrahydrofuran,ethilazitate, benzol and homolog, alkyl benzene (C₉ and C₁₀), alkanes(C₇-Ci i), ethylene (C₇-Ci₀), terpene (C_(I-O)) and naphthalene(C_(I-O)). Partial destruction of outer functional groups takes place at573K. During this process nitromethane, butanone, tetrahydrofuran,ethylatite, presumably, acentonitrile. However main quantity ofidentified compositions: benzol and homolog, alkanes, alkenes, terpeneand naphthalene—possessing special character and structure, may formonly at x-ray amorphous carbon phase destruction that is verified byfact of samples mass reduction after thermal desorption ˜8 mass. %.Temperature of nanodiamonds oxidations beginning in openair—gasification temperature, measure by derivathograph at heating speed10 deg/min,

is 473K, and small exo-effect is observed till 800 K. All non-diamondx-ray amorphous carbon is being oxidated at this. The sample weightreduction is 5-18 mass. %, corresponding with x-ray carbon quantity innano-diamond.

After heating over 800K strong exo-effect is observed. This testifiesabout reaction of air oxygen with diamond nuclei of nano-diamond that isover at 1050K by nanodiamond full oxidation (burning out). Maximum heatdischarge (maximum oxidation) take place at 930-990K.

The research of crystal diamonds of static synthesis (ASM), smashed intoparticles s2-100 nm in size (with average diameter of 20 nm), put intoconditions alike, were carried out. Research showed that the temperatureof the diamond crystal oxidation process beginning is 785K, but maximumoxidation temperature is 890K. Full oxidation process of ASM is over at1060K. So, oxidation resistance of classic diamond and nanodiamond,according to given invention, and classic synthetic diamonds is almostthe same.

Nanodiamond, produced by method according to closest analogue, has itsdiamond nuclei oxidated at 703K.

Every particle of nanodiamond on given invention is complicatedstructural formation, including the following elements as compulsorycomponents:

-   -   carbon atoms nuclei sp³-hybrydaized, connected into cubic        crystal structure, typical for diamonds; nuclei covers 82-95% of        carbon atoms and posses due to x-ray-graphy size of 40-50 A;        nuclei has 2.5 mas. % nitrogen, mainly in form of substitution        atoms; transition carbon cover around the nuclei, consisting        from x-ray amorphous structures of carbon with width of 2-4 A,        which can contain 5-18% of carbon atoms of a particle. The        cover, consisting of carbon in sp-hybridization, not uniform.        Internal layer of this cover, directly adjoining nuclei, form        continuous onion-like carbon layers, fragmented, graphite-like        layers (aromatic clusters) located above them.

This amorphous carbon cover possess porous structure, various defects,includes small quantity of heteroatoms (first of all—2.5 mass. %nitrogen), entered the cover structure in process of detonationsynthesis;

-   -   surface layers, containing other heteroatoms except carbon        atoms, forming specter of different functional groups        (hydroxyl-, carbonyl-, carboxyl, nitrile and methal groups)        Overall quantity of heteroatoms in particle—nitrogen, hydrogen        and oxygen—is form 2.0 to 9.8 mass, %. Thus, it was determined        that nanodiamonds are not pure carbon material. Carbon exists in        the product simultaneously in different modifications and only        one of them corresponds to diamond structure. Outer cover of        nanodiamond particle determines its relation with environment.        That is it that forms the phase interface and takes part in        interacting with it. Presence at surface of highly-polar and        reaction-capable groupings, concentrated in small volume,        determines sufficient influence activity of nanodiamond        particles onto environment. Nanodiamond, produced on given        invention, is unique material due to its transitional nature        from inorganic product to organic and this determines their        special position among ultradispersed materials.

INDUSTRIAL USE

Nanodiamond, produced by method according to invention, allows it use asnanosize component of high-efficacy composite materials as additives,improving exploitation characteristics of constructions—endurance,durability, resource—more then from use of nanodiamonds, known fromabove described previous technical level.

Nanodiamonds, according to invention, can be produced by methodaccording to invention, which can be realized with help of existingtechnological equipment and known explosives.

1. Nanodiamond, containing carbon, hydrogen, nitrogen and oxygendiffered by content of carbon in form of diamond cubic modification andx-ray amorphous phase carbon with ratio (82-95):(18-5) mass. % on carbonmass, correspondingly, and contains, mass. %: Carbon 90.2-98.0 Hydrogen0.1-5.0 Nitrogen 1.5-3.0 Oxygen 0.1-4.5.
 2. Nanodiamond productionmethod, including carbon-containing explosive with negative oxygenbalance detonation in closed volume and in gauzy, carbon inertenvironment, surrounded by condensed phase and later chemicalrefinement, different by detonation of carbon-containing explosive, putinto condensed phase cover, containing deoxidizer with quantitativeratio of deoxidizer mass in condensed phase and mass of usedcarbon-containing explosive not less then 0.01:1. Chemical refinement isrealized by treatment of products by 2-40% water nitric acid alone withcompressed air oxygen at 200-280° C. and pressure 5-15 MPa. Producednanodiamond contain, mass. %: Carbon 90.2-98.0 Hydrogen 0.1-5.0 Nitrogen1.5-3.0 Oxygen 0.1-4.5 and in carbon mass containing carbon of diamondcubic modification and carbon in x-ray amorphous phase with ratio of(82-95):(18-5) mass. %, respectively.
 3. Method on p. 2 differs by useof inorganic or organic composition as deoxidizer, preferably notcontaining oxygen atoms and halogen.